#app{
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  background-color: skyblue;
}

.box{
  position: relative;
  width: 100px;
  height: 100px;
  border: 1px solid #1aa034;
  left: 0;
  top: 0;
  transition: all .5s;
}

.enter{
  transform: rotate(90deg);
  border-color: pink;
}
